The goal of this proposal is to develop tumor necrosis factor (TNF)-inhibiting compounds as neuroprotectant drugs for treating Alzheimer's disease (AD). Current FDA-approved AD interventions are symptomatic treatments with limited efficacy which do not affect AD etiology or modify the course of disease progression. Thus, a critical need exists for a novel AD treatment directed towards AD pathophysiology. Recent studies implicate the neuroinflammatory cytokine TNF- as a key mediator in AD- associated neurodegenerative pathology. Multiple preclinical and clinical studies indicate that TNF is a druggable molecular target to modify the course of AD progression. P2D, inc. is developing a novel TNF inhibitor, PD2015 (3,6' dithiothalidomide), a dithionylated analog of thalidomide as an anti-AD drug candidate for in vivo efficacy testing in a mouse model of AD. PD2015 exhibits 1800% greater TNF inhibition in vitro than its parent, thalidomide. The applicant organization recently published work demonstrating the efficacy of PD2015 in 3xTg AD mice [52]. A 50 mg/kg PD2015 i.p. dose administered daily for two months significantly improved working memory (*P<0.05) in 3xTg AD mice. PD2015 also significantly modulated brain TNF levels after daily treatment for two months in 3 x Tg AD mice. Recent preliminary studies with chronic oral PD2015 dosing (50 mg/kg) demonstrate improved cognition. In contrast, thalidomide did not improve working memory or block brain TNF levels in 3 xTg AD mice. Taken together, these data strongly suggest that PD2015 is a good anti-AD drug candidate. The proposed preclinical study is designed to evaluate the oral efficacy of chronic low doses of PD2015 administration across a 12-fold dose range in symptomatic 6 mo. old 3xTg AD mice. Specific Aim 1A): Determine the effect of chronic oral administration of PD2015 on cognitive function in 3xTg AD mice. Specific Aim 1B): Determine the effect of PD2015 on indicators of neuroinflammation and AD- associated pathology including TNF- levels, Ass1-40/Ass1-42 levels, microglial activation, tau, phospho-tau, synaptophysin, SNAP-25 in 3xTg AD mice.